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markom |
'\"
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'\" Copyright (c) 1992-1994 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: CrtGenHdlr.3,v 1.1.1.1 2002-01-16 10:25:48 markom Exp $
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'\"
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.so man.macros
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.TH Tk_CreateGenericHandler 3 "" Tk "Tk Library Procedures"
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.BS
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.SH NAME
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Tk_CreateGenericHandler, Tk_DeleteGenericHandler \- associate procedure callback with all X events
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.SH SYNOPSIS
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.nf
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\fB#include \fR
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.sp
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\fBTk_CreateGenericHandler\fR(\fIproc, clientData\fR)
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.sp
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\fBTk_DeleteGenericHandler\fR(\fIproc, clientData\fR)
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.SH ARGUMENTS
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.AS "Tk_GenericProc" clientData
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.AP Tk_GenericProc *proc in
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Procedure to invoke whenever any X event occurs on any display.
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.AP ClientData clientData in
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Arbitrary one-word value to pass to \fIproc\fR.
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.BE
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.SH DESCRIPTION
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.PP
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\fBTk_CreateGenericHandler\fR arranges for \fIproc\fR to be
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invoked in the future whenever any X event occurs. This mechanism is
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\fInot\fR intended for dispatching X events on windows managed by Tk
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(you should use \fBTk_CreateEventHandler\fR for this purpose).
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\fBTk_CreateGenericHandler\fR is intended for other purposes, such
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as tracing X events, monitoring events on windows not owned by Tk,
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accessing X-related libraries that were not originally designed for
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use with Tk, and so on.
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.PP
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The callback to \fIproc\fR will be made by \fBTk_HandleEvent\fR;
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this mechanism only works in programs that dispatch events
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through \fBTk_HandleEvent\fR (or through other Tk procedures that
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call \fBTk_HandleEvent\fR, such as \fBTk_DoOneEvent\fR or
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\fBTk_MainLoop\fR).
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.PP
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\fIProc\fR should have arguments and result that match the
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type \fBTk_GenericProc\fR:
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.CS
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typedef int Tk_GenericProc(
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ClientData \fIclientData\fR,
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XEvent *\fIeventPtr\fR);
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.CE
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The \fIclientData\fR parameter to \fIproc\fR is a copy of the \fIclientData\fR
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argument given to \fBTk_CreateGenericHandler\fR when the callback
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was created. Typically, \fIclientData\fR points to a data
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structure containing application-specific information about
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how to handle events.
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\fIEventPtr\fR is a pointer to the X event.
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.PP
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Whenever an X event is processed by \fBTk_HandleEvent\fR, \fIproc\fR
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is called. The return value from \fIproc\fR is normally 0.
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A non-zero return value indicates that the event is not to be handled
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further; that is, \fIproc\fR has done all processing that is to be
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allowed for the event.
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.PP
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If there are multiple generic event handlers, each one is called
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for each event, in the order in which they were established.
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.PP
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\fBTk_DeleteGenericHandler\fR may be called to delete a
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previously-created generic event handler: it deletes each handler
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it finds that matches the \fIproc\fR and \fIclientData\fR arguments. If
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no such handler exists, then \fBTk_DeleteGenericHandler\fR returns
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without doing anything. Although Tk supports it, it's probably
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a bad idea to have more than one callback with the same
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\fIproc\fR and \fIclientData\fR arguments.
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.PP
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Establishing a generic event handler does nothing to ensure that the
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process will actually receive the X events that the handler wants to
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process.
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For example, it is the caller's responsibility to invoke
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\fBXSelectInput\fR to select the desired events, if that is necessary.
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.SH KEYWORDS
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bind, callback, event, handler
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